What Is a Strainer?
A Strainer is a component that removes fine particles from a liquid or gas. A similar component is a line filter, but it has a different application.
Strainers are inserted upstream of equipment to protect the equipment, whereas line filters are installed to filter and normalize the fluid.
Uses of Strainers
Strainers are used in consumer products, such as automobiles. They are installed upstream of the engine in engine oil lines to provide engine protection. Other applications include sewer piping.
For industrial applications, they are often used in plants and hydraulic units. They are installed upstream of equipment such as pressure reducing valves and pumps, mainly to prevent the entrapment of foreign matter.
There are also two types of strainers: products for periodic cleaning of internal screens and temporary strainers.
Temporary strainers are disposable strainers. They are basically removed after the piping work is completed. They are available in cone and plug-in types.
Principle of Strainer
A strainer consists of a body, an O-ring, and a screen. The screen is contained in the body and is connected to the piping with an O-ring to prevent leakage. The most important part is the screen, which is made of perforated metal or mesh in the shape of a mesh.
The size of the foreign matter to be removed is determined by selecting the mesh coarseness. If the foreign material is large, the screen mesh should be coarser; if it is small, the screen mesh should be finer. There are also Y-type and U-type strainers. Basically, the Y type is used for small flow rates and the U type for large flow rates.
The pressure loss of the strainer should be noted. Installing a Strainer causes a pressure loss, and if a fine-meshed strainer is installed at the inlet of the pump, cavitation may occur.
Other Information on Strainers
1. Cleaning the Strainer
Since the Strainer uses a filter to remove debris from the fluid, debris accumulates inside. If not cleaned regularly, the filter will become clogged, resulting in various problems. The most common cleaning method is to remove the internal filter and flush it with water.
The cleaning operation is carried out by cutting off the edges at the inlet and outlet valves of the Strainer. If the line cannot be easily shut down, provide a bypass line to the Strainer in advance for cleaning. Strainer clogging is detected by monitoring the discharge pressure of the pump in the line.
It is also important to inspect the Strainer before operation, as foreign matter in the line may flow into the Strainer after a long shutdown.
2. Mesh of Strainer
In Strainers, filter roughness is generally expressed in terms of mesh. Mesh is the number of meshes in one inch. If there are 10 meshes in an inch, it means 10 meshes. In reality, there are 10 meshes in each 1″ x 1″ square, so there are 100 meshes in a 1″ square.
Strainers with double-layered filters are also available. In a dual structure filter, a coarse filter is installed on the outside and a fine filter is installed on the inside. Strainer coarseness and construction are selected based on discussions with the manufacturer and past performance.